Rails - Jun 2006 - Sortable list with non ajax submission

I am trying to create a sortable list that is submitted not with an AJAX 
call but by a standard form submit button.
Right now I have

def reorder_group_members
    @group = Group.find(params[:id])
    @group.group_members.each do |member|
      member.position = params[:memberlist].index(member.id.to_s) + 1    
#I get a nil error for this line.  It would seem that 
params[:memberlist] is not getting set.
      member.save
    end
    render :action => ''index''
end

with view

<%=start_form_tag  :action=>''reorder_group_members'', :id
=> @group%>
  <ul class="group_members" id="memberlist" 
style="height:150px;width:200px;">
  <% for member in @group.group_members-%>
    <li
id="memberlist_<%=member.id%>"><%=member.name%></li>
  <%end%>
  </ul>
  <%=submit_tag%>
<%=end_form_tag%>
<%= sortable_element ''memberlist'' -%>

This works fine in terms of the member list being sortable by dragging 
but when I click the submit button I get a nil error because the sorting 
information is not being passed as a paramater.  Any ideas?

Thank you,
Matthew Margolis
blog.mattmargolis.net